The use of a photosensitive resin composition as a printing plate has been a common practice, and has become mainstream in various fields, such as letterpress printing, lithography printing, intaglio printing, etc.
A photosensitive resin printing plate is used as follows. That is, a negative or positive original image film is placed in close contact with the photosensitive layer of the printing plate, and a ray of active light is applied thereto through the original image film so as to form in the photosensitive layer a latent image made up of solvent-soluble portions and solvent-insoluble portions, or hardened portions and non-hardened portions. By developing the latent image, a relief image is formed, so that the plate can be used as a printing plate. Development methods employed for photosensitive resin printing plate materials include a method in which unexposed portions are blown off by using compressed air or the like, a method in which unexposed portions are removed by jetting a developer at a fixed pressure in a spray fashion, and a method in which unexposed portions are rubbed off by using a brush or the like while immersing the plate in a developer or jetting a developer in a shower fashion.
According to the developing method for a photosensitive resin printing plate material in which unexposed portions are rubbed off by using a brush or the like while immersing the plate in a developer or jetting a developer in a shower fashion, photosensitive resin layer components from the rubbed-off unexposed portions exist in a dissolved or dispersed state in the developer. If such a developer liquid is reused repeatedly to develop photosensitive resin printing plate materials, the concentration of photosensitive resin layer components in the developer increases, resulting in the problems of reduced developing speed, deposition of photosensitive resin layer components aggregated from the dispersed state on a printing plate or the brush of the developing machine, etc. Therefore, it is required that the developer be frequently replaced and the developer containing at least a certain level of photosensitive resin layer components be discarded as a waste liquid. Hence, the method suffers high costs of waste liquid disposal. Furthermore, due to large production of waste, the method also has problems in terms of environment protection.
Therefore, as a technique for reducing the environmental load, a closed-cycle method of reusing a developer used in the developing step is demanded. The closed-cycle methods proposed include, for example, a method in which dispersed photosensitive resin layer components are removed from a developer containing photosensitive resin layer components, a method in which aggregates are removed from a developer, for example, through the use of a filter or the like (Japanese Patent Application Laid-Open Publication No. 7-333861), a method in which photosensitive resin layer components in a developer are aggregated by adding a flocculating agent to the developer (Japanese Patent Application Laid-Open Publication No. 2001-47060), etc. However, the method in which photosensitive resin layer components are removed via a filter is not practical since the filter is soon clogged with photosensitive resin layer components. According to the method in which a flocculating agent is added, the flocculating agent is contained in the developer to be reused, thus resulting in the following problems. That is, the developing speed decreases, and photosensitive resin layer components produced during the development aggregate and deposit on a printing plate or the brush of the developing machine.
Thus, there is a need for a method for making a photosensitive resin printing plate in which a developer produced as a result of the step of developing a photosensitive resin printing plate material, more particularly, a developer produced as a result of the development of an aqueous-developable photosensitive resin printing plate material, is reused without a reduction in the developing speed nor aggregation of a photosensitive resin layer component, and also an apparatus for processing a developer produced as a result of the step of developing a photosensitive resin printing plate material.